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CREATE TABLE sys_sequence (  seq_name VARCHAR(50) NOT NULL,  curr_value BIGINT NOT NULL DEFAULT 0,  increment_by INT NOT NULL DEFAULT 1,  PRIMARY KEY (seq_name)) ENGINE=INNODB;
    
    
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INSERT INTO sys_sequence VALUES ('SEQ_TEST_NO', 10000, 1);
    
    
currval????
  
    
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DELIMITER $$DROP FUNCTION IF EXISTS currval $$CREATE FUNCTION currval(v_seq_name VARCHAR(50)) RETURNS BIGINT CONTAINS SQL BEGIN  DECLARE v_currval BIGINT;  SET v_currval = 1;  SELECT curr_value INTO v_currval   FROM sys_sequence   WHERE seq_name = v_seq_name;  RETURN v_currval;END$$DELIMITER ;
    
    
nextval????
  
    
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DELIMITER $$DROP FUNCTION IF EXISTS `nextval` $$CREATE FUNCTION `nextval` (`v_seq_name` VARCHAR(50)) RETURNS BIGINT (20) CONTAINS SQL BEGIN  UPDATE sys_sequence   SET `curr_value` = LAST_INSERT_ID(`curr_value` + `increment_by`)   WHERE `seq_name` = v_seq_name;  RETURN LAST_INSERT_ID();END$$DELIMITER ;
    
    
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currval('SEQ_TEST_NO') - ???????
    
     
nextval('SEQ_TEST_NO') - ???????????